382 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 26, 



rence, in the upper part especially. This structure is best exhibited 

 around Woking, Horsley, and White Hill near Egham. A peculiar 

 local instance in these lower Bagshot sands of their sudden transition 

 into, or rather of the sudden substitution of clays, occurred at the 

 railway-cutting at Goldsworthy Hill near Woking. Immediately 

 under the central green sands, the upper part (for a depth of five or 

 six feet, which was as far as it was exposed) of the underlying fine 

 white siliceous sands were there seen passing horizontally and abruptly 

 into a dark grey laminated clay (see Fig. 3. at point marked "2/")' 



This variation of structure is of very local character, as this bed of 

 clay does not even appear at the outcrop of the same sands on the 

 south side of the hill at less than a quarter of a mile distant. To the 

 north however it is apparently more persistent, and it is probable that 

 part of the neighbourhood of Chobham, which stands on the upper 

 beds of the lower sands, is in some measure indebted to the occasional 

 presence of this bed for its good supply of water and general fertility. 



In the western districts of the Bagshot sands this lower division 

 again becomes very argillaceous, passing into light brown loams. 

 Their lowest beds remain however usually the most sandy. 



Amongst the subordinate lithological characters is the frequent pre- 

 sence in the sands of small plates of mica (especially where slightly 

 laminated with clays), of large grains of yellow and transparent quartz, , 

 pebbles of black rolled flints, thin layers and nodules of iron sand- 

 stone, and a few concretionary masses of saccharine sandstone, which 

 are more compact and harder than those in the upper sands, and by 

 no means so abundant. 



The following section exhibits the details of the divisions and the 

 general structure of the Bagshot sands : — 



Fig. 3. 



tt- Upper Bagshot Sands. ieet- 



Yellow and light ochreous siliceous sands. A few casts of Turritella, Cardium, Natica 

 Ostrea and Nummulites are of very rare and local occurrence. Sandstone concretions 

 at "o " 150 



b. Middle Bagshot Sands. 



1 . Coarse greenish sand with a few flint pebbles 2 



2. Foliated sandy clays of various shades of brown 11 



